What's the Difference Between Sith Lords, Darths, and Dark Lords of the Sith

I was just wondering, its confusing from the 6 films and playing games such as SWTOR, what is the rank difference between Sith Lords, Darths, and Dark Lords of the Sith, as Lords and Darths seem like the same thing, i just want it clarified

Everything you listed in the title/OP is exactly the same thing, the only exception being SOME Sith Lords did not go by the Darth title system and/or some Dark Lords were may have not been acknowledged as being Sith.

Except that *Darth* is given to those who are [keywords]acknowledged[/keywords] as being *Sith* by their *Masters*, otherwise everything else is true, except for Dark Jedi who are like --- tweeners or something